Mask of Destiny — Marianne Andrau

A glamorous city...where terror awaited. Natalie's decision to work in Monte Carlo for the summer thrust her into a strange glittering world. There she met Ramona, a millionaire's daughter -- and a woman dangerously obsessed with gambling. Impulsively she tried to help when Ramona confided a terrible secret: she was being blackmailed. Natalie was sure they could outwit the scoundrel. But soon she, too, was drawn into a whirl of deceit that spun her faster and faster toward ruin.